Check variable in parent scope, an interesting approach to testing a parent if condition.

condition-check.Tests.ps1

Get-Module m | Remove-Module
New-Module -Name m -ScriptBlock { 
    function Do-Expensive { }
} | Import-Module 

function f () {
    $variable = 2
    # if ($variable -eq 1) {
        Do-Expensive
    # }
}


Describe "a" { 
    It "b" { 
        Mock -CommandName "Do-Expensive" -MockWith { 
            if ($variable -ne 1) {
                throw "Variable `$variable is not 1, it is $($variable)."
            }
            else { 
                Write-Host "Variable `$variable is 1."
            }
        }

        f
    }
}